2023-05-17 09:25:16

by Peng Zhang

Subject: [PATCH v2 04/10] maple_tree: Simplify mas_is_span_wr()

Make the code for detecting spanning writes more concise.

Signed-off-by: Peng Zhang <[email protected]>
---
lib/maple_tree.c | 42 ++++++++++++++----------------------------
1 file changed, 14 insertions(+), 28 deletions(-)

diff --git a/lib/maple_tree.c b/lib/maple_tree.c
index bec9906b0c8c..82dccc660889 100644
--- a/lib/maple_tree.c
+++ b/lib/maple_tree.c
@@ -3728,43 +3728,29 @@ static inline void mas_store_root(struct ma_state *mas, void *entry)
*/
static bool mas_is_span_wr(struct ma_wr_state *wr_mas)
{
- unsigned long max;
+ unsigned long max = wr_mas->r_max;
unsigned long last = wr_mas->mas->last;
- unsigned long piv = wr_mas->r_max;
enum maple_type type = wr_mas->type;
void *entry = wr_mas->entry;

- /* Contained in this pivot */
- if (piv > last)
+ /* Contained in this pivot, fast path */
+ if (last < max)
return false;
-
- max = wr_mas->mas->max;
- if (unlikely(ma_is_leaf(type))) {
- /* Fits in the node, but may span slots. */
- if (last < max)
- return false;
-
- /* Writes to the end of the node but not null. */
- if ((last == max) && entry)
- return false;
-
+ if (ma_is_leaf(type))
+ max = wr_mas->mas->max;
+ if (last < max) {
+ /* Contained in this pivot or this leaf node */
+ return false;
+ } else if (last == max) {
/*
- * Writing ULONG_MAX is not a spanning write regardless of the
- * value being written as long as the range fits in the node.
+ * The last entry of leaf node cannot be NULL unless it is the
+ * rightmost node (writing ULONG_MAX), otherwise it spans slots.
+ * If this is not leaf node, detect spanning store wr walk.
*/
- if ((last == ULONG_MAX) && (last == max))
- return false;
- } else if (piv == last) {
- if (entry)
- return false;
-
- /* Detect spanning store wr walk */
- if (last == ULONG_MAX)
+ if (entry || last == ULONG_MAX)
return false;
}
-
- trace_ma_write(__func__, wr_mas->mas, piv, entry);
-
+ trace_ma_write(__func__, wr_mas->mas, wr_mas->r_max, entry);
return true;
}

--
2.20.1

2023-05-17 18:39:39

by Liam R. Howlett

Subject: Re: [PATCH v2 04/10] maple_tree: Simplify mas_is_span_wr()

* Peng Zhang <[email protected]> [230517 04:59]:
> Make the code for detecting spanning writes more concise.
>
> Signed-off-by: Peng Zhang <[email protected]>
> ---
> lib/maple_tree.c | 42 ++++++++++++++----------------------------
> 1 file changed, 14 insertions(+), 28 deletions(-)
>
> diff --git a/lib/maple_tree.c b/lib/maple_tree.c
> index bec9906b0c8c..82dccc660889 100644
> --- a/lib/maple_tree.c
> +++ b/lib/maple_tree.c
> @@ -3728,43 +3728,29 @@ static inline void mas_store_root(struct ma_state *mas, void *entry)
> */
> static bool mas_is_span_wr(struct ma_wr_state *wr_mas)
> {
> - unsigned long max;
> + unsigned long max = wr_mas->r_max;
> unsigned long last = wr_mas->mas->last;
> - unsigned long piv = wr_mas->r_max;
> enum maple_type type = wr_mas->type;
> void *entry = wr_mas->entry;
>
> - /* Contained in this pivot */
> - if (piv > last)
> + /* Contained in this pivot, fast path */

Thanks for adding the fast path comment here.

> + if (last < max)
> return false;
> -

Please have new lines after an if statement

> - max = wr_mas->mas->max;
> - if (unlikely(ma_is_leaf(type))) {
> - /* Fits in the node, but may span slots. */
> - if (last < max)
> - return false;
> -
> - /* Writes to the end of the node but not null. */
> - if ((last == max) && entry)
> - return false;
> -
> + if (ma_is_leaf(type))
> + max = wr_mas->mas->max;

New line here too

> + if (last < max) {
> + /* Contained in this pivot or this leaf node */
> + return false;

Since you have the last < max check earlier, this is only needed in the
if(mas_is_leaf()) statement above. Making the below else if() an if()
should work.

> + } else if (last == max) {
> /*
> - * Writing ULONG_MAX is not a spanning write regardless of the
> - * value being written as long as the range fits in the node.
> + * The last entry of leaf node cannot be NULL unless it is the
> + * rightmost node (writing ULONG_MAX), otherwise it spans slots.
> + * If this is not leaf node, detect spanning store wr walk.
> */
> - if ((last == ULONG_MAX) && (last == max))
> - return false;
> - } else if (piv == last) {
> - if (entry)
> - return false;
> -
> - /* Detect spanning store wr walk */
> - if (last == ULONG_MAX)
> + if (entry || last == ULONG_MAX)
> return false;
> }
> -
> - trace_ma_write(__func__, wr_mas->mas, piv, entry);
> -
> + trace_ma_write(__func__, wr_mas->mas, wr_mas->r_max, entry);
> return true;
> }
>
> --
> 2.20.1
>